Hall sensors accurate in 30 tesla fields, cryogenic temperatures

October 24, 2021 // By Peter Clarke
Hall sensors accurate in 30 tesla fields, cryogenic temperatures
Graphene-based sensor developer Paragraf Ltd. (Cambridge, England) has produced a Hall Effect sensor has extended the range of conditions under which it sensors operate.

Tested at the High Field Magnetic Laboratory (HFML) at Radboud University Nijmegen, the GHS-C sensors support operation in magnetic fields up to 30 tesla and at temperatures down to 1.5K. The sensors deliver a degree of accuracy that has not previously been achievable under these conditions, sustaining non-linearity errors of significantly less than 1 percent across the full measurement range, the company claims.

The devices set benchmarks in linearity and output symmetry, thereby opening up an array of potential application opportunities, the company added.

The magnetic field measurement capabilities of the GHS-C devices are due to the graphene sensor elements. Graphene's inherent high electron mobility directly translates into high sensitivity capability, which is maintained across the entire magnetic field range – making these devices simpler to calibrate

The two-dimensional nature of graphene also means high quality, repeatable and accurate data is provided by the GHS-C sensor, with no hysteresis and immunity to in-plane stray fields. This is a step beyond conventional Hall sensors which have demonstrated asymmetry, producing different measurements depending on field direction.

A further advantage of the GHS-C range is their low power operation resulting in power dissipation that is in the nanowatt range, compared to micro- or milliwatts associated with non-graphene Hall sensors.

Examples of suitable applications include low temperature quantum computing, high-field magnet monitoring in next generation MRI systems, fusion energy field control, particle accelerators, and other scientific and medical instrumentation. The sensors can also be directly used in fundamental physics experiments e.g., quantum physics research, superconductivity and spintronics.

"Under cryogenic temperatures and in extremely high magnetic fields, the sensitivity performance of other high-end Hall sensors drops off acutely. This is due to interactions occurring between the different layers of the sensor element. It leads to linearity issues that curb their range, as well as making them incredibly difficult to calibrate. Consequently, the best achievable accuracy of these sensors becomes significantly limited above around 16T," states

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